A number of papers, for example Jigesh K. Patel, Sung U. Kim, David H. Su, Suresh Subramaniam, Hyeonig-Ah Choi “A Framework for Managing Faults and Attacks in WDM Optical Networks”—supported in part by the DAPRA under grant N66001-00-18949 and Shut-Kit Chan, Frank Tong, Lian-Kuan Chen, Dennis Lam “Demonstration of a Fault-Tolerant WDM add-drop/branching Unit for Long Haul Optical Transmission Systems”. IEEE Photonics Technology Letters, vol 11, No. 8, August 1999 discuss a problem of managing faults and attacks in WDM optical networks, and a model of a fault-tolerant add-drop branching unit. Such a unit is planned to detect fiber cuts and failures of optical amplifiers. All operations performed in the discussed unit are based on checking and comparing power of the received, added and dropped signals.
US patent application 2004/0175179 describes a self-adjusting optical add-drop multiplexer (OADM), and optical network using same. The self-adjusting optical add-drop multiplexer monitors the power in a drop signal and attenuates the power in an add signal to match the power in express WDM channels (signals). When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. Power attenuation is also used in an optical switching assembly particularly useful in two-fiber ring network. The optical switching assembly monitors drop channels from the two rings of the network and attenuates the add channel(s) accordingly. An optical switch operates to direct the drop signal from one of the two rings to a receiver in accordance with a control signal based on the monitored drop channels. The self-adjusting optical add-drop multiplexer also monitors the power in the drop signals and issues an alarm if the drop signal is of a power level above or below predetermined levels.
It should be noted that the above self-adjusting OADM sets a task of adjusting (equalizing) powers of added, dropped and through channels. It does not pay any attention at all to a possibility of penetration, into the optical network, of a signal having a wrong (or non-exact) optical wavelength, or an optical wavelength issued from a foreigner source.
US published patent application 2004/0109685 A1 describes an OADM comprising a demultiplexer wherein each optical channel is being marked with a pilot tone for channel identification and monitoring. The pilot tones are detected, cleaned from ghost tones, and then re-inserted in the respective optical channels being fed into the multiplexer of the OADM, for multiplexing said optical channels into a WDM output signal.
The above-mentioned 2004/0109685 A1 is intended for monitoring the presence or absence of different optical channels in the network for purposes of management; it does not consider a task of channel authentication and/or security in optical networks. The problem of authentication of optical channels becomes especially important when optical networks utilize novel reconfigurable OADMs.
To the best of the Applicant's knowledge, solutions to such a problem have not been considered in the prior art.